The present invention relates to scroll compressors. More specifically, the present invention relates to the controlled flow of lubricant and suction gas in and through a hermetic low-side refrigerant scroll compressor.
Low-side compressors are compressors in which the motor by which the compressor's compression mechanism is driven is disposed in the suction pressure portion (low-side) of the compressor shell. In the case of a scroll compressor, the motor most often drives one of the two scroll members which comprise the compressor's compression mechanism and which are constrained, by use of a device such as an Oldham coupling, to relative motion such that one scroll member orbits with respect to the other.
Such orbital motion, in the proper direction, causes the cyclical creation of pockets at the radially outward ends of the interleaved involute wraps of the scroll members. During compressor operation, such pockets fill with suction gas, close and are displaced radially inward while decreasing in volume thereby compressing the gas trapped in them. The compression pockets are ultimately displaced into communication with a discharge port, most often located at the center of the scroll set, and the compressed gas is expelled therethrough.
In low-side scroll compressors used in refrigeration applications, relatively oil-free refrigerant gas at suction pressure must be delivered to the vicinity of the suction pockets that are cyclically defined at the radially outward ends of the wraps of the scroll members. At the same time, however, provision must be made for the lubrication of the bearings in which the drive shaft and driven scroll member rotate as well as for the lubrication of other components and surfaces in the suction pressure portion of the compressor shell. As a result, the delivery of lubricant to surfaces requiring lubrication in the low-side of the shell of a refrigeration scroll compressor, its return to the lubricant sump therein and the interaction of such lubricant with the suction gas flowing to the compression mechanism therethrough must be carefully managed and controlled so as to maximize compressor efficiency while providing adequate lubrication where and when needed.
One arrangement by which suction gas and lubricant flow are controlled in a low-side scroll compressor is taught in U.S. Pat. No. 5,533,875, assigned to the assignee of the present invention and incorporated herein by reference. In that arrangement, use is made of a sleeve mounted in the suction pressure portion of the compressor shell and in which the compressor drive motor is mounted so as to control and isolate lubricant and suction gas from each other as they flow through the low-side of the compressor. The use of such a sleeve, while effective, brings with it certain disadvantages and costs both in terms of the compressor's material cost and in terms of the compressor assembly process.